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SS Deeb, T Hayashi; Mutually Exclusive Expression of the Red and Green Visual Pigment Genes in the Human Cone-derived Retinoblastoma Cell Line WERI . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3646.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate whether expression of the red and green photopigment genes in the cone-derived human retinoblastoma cell line WERI mimics that in human retinal cones. Methods: The presence of red and green pigment mRNAs in single cells, doublets or clusters of cells was determined by reverse transcription followed by PCR amplification of exons 2-5. A second round of amplification using gene-specific primers was used to determine if the mRNA encoded red or green photopigments. Single strand conformation polymorphism was used to distinguish between different green pigment alleles. Results: WERI cells were derived from a female and were confirmed to contain two X-chromosomes. Only one of the X-chromosomes, which carries a visual pigment gene array composed of one red and at least two green pigment genes, was transcriptionally active in all cells. A single WERI cell (N=35) expressed a single pigment gene into either red or green pigment mRNA. This mutually exclusive pattern of expression of the visual pigment gene array was previously observed in retinal cones. As a single WERI cell divided to form a doublet and a cluster of daughter cells, expression was observed to switch from red to green pigment mRNA and visa versa, indicating that DNA replication resets the commitment to express either the red or geen pigment genes of the array. For example, 41% (N=44) of doublet cells expressed two pigment genes, and the majority of cell clusters (12/13) expressed red and green pigment genes. Interestingly, the red plus two of the green pigment genes of the array are expressed among WERI cells. This differs from the observed expression of only two genes of any given array among the red and green cones of the human retina. Conclusion: The expression of either the red or green pigment genes in a single WERI cell mimics the mutually exclusive expression of these pigments in human photoreceptor cones. Cell division resets this selective gene expression in individual cells. Therefore, this cell line would be valuable for studies of the mechanism and factors that assure mutually exclusive expression of pigment genes of an array in photoreceptor cones, which is fundamental to color vision.
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